This invention relates generally to digital emulation systems and specifically to a digital emulation system using multiple logic processors with improved signal routing.
As electronic circuit designs continue to increase in speed and complexity, it becomes ever more critical to test the developing circuit designs at various stages of development. Hardware emulators provide a means to test complex circuit designs as the designs are being developed. Such emulators typically provide configurable hardware that is controlled by software to perform the functions of a circuit being designed. The circuit design is specified by a set of data which defines the circuit structure and behavior.
Emulators operate under software control. The circuit design is "compiled" to produce the program that controls the emulator. The process of compiling the design to produce the program for the emulator is a critical and lengthy process. A lengthy compile time is due, in part, to the goal of producing a program that emulates the circuit design as fast as possible. Speed is of the essence in emulators because inevitably the emulator cannot perform the functions of the circuit being emulated as quickly as the actual circuit, itself. It is desirable to operate the emulator at speeds as close as possible to the target operating speed of the emulated circuit for purposes of accurately interfacing the design to external circuits or other devices and to test the circuit for timing problems.
Another reason why the compilation step is complex and time consuming is that constraints in the hardware of the emulator make it difficult to optimize the program for speed without making many computations during compilation. Since an emulator must perform the functionality of a wide range of circuit designs ! it should be as flexible as possible. This means the emulation system must contain logic processing hardware that is reusable for different designs. Such an emulation system would contain a large number of general purpose processing elements that are used to indirectly perform the function of the circuit being emulated. For example, a general purpose emulator would process multiple boolean logic equations to emulate a multiplier circuit rather than use a dedicated hardware multiplier for the same purpose which would then become unusable in the emulation of circuit designs which do not contain any multiplier functions. In order to solve these equations, many gates, or other devices, in the emulator must be provided with signals. Further, the outputs of the gates or other components must be routed efficiently among the various components of the emulator.
Even though the compilation step is complicated and lengthy, it is necessary to make this step as brief as possible so that a human designer does not have to wait a long time before emulating the latest design change. This is especially important where emulators are used in the design and development of integrated circuits. Many incremental changes are made, each of which requires a compilation step before emulation can proceed. This implies that the time of the compilation step should be shortened in order to increase the utility of the emulator.
Therefore, it is desirable to produce an emulator that provides for short compilation times and that produces an emulation program capable of emulating a circuit design at a high speed.